多輸入多輸出正交分頻多工與分碼多重進接收發機之共同設計

Abstract

隨著通訊技術的進步，提供高速傳輸服務之無線通訊系統已成為近年來的研究主題之一。多輸入多輸出技術可用來在空間中創造獨立的平行通道，用以傳送不同資料串流，以提升系統的整體傳輸速率。多輸入多輸出技術所提供的此種空間多工技術可在不需佔用額外頻譜資源的前題下，大幅地提升頻譜效率。另一方面，正交分頻多工與分碼多重進接為目前無線通訊系統普遍採用的兩種傳輸技術。在本論文中，吾人將探討多輸入多輸出正交分頻多工與分碼多重進接收發機之共同設計。此共同設計的核心理念是將正交分頻多工的子載波與分碼多重進接的展頻碼視為互相對應的部分。吾人將探討此共同設計所需之通道估測、時序同步與載波頻率飄移估測等方法。具體而言，吾人將提出具有較大估測範圍之載波頻率飄移估測法，與需較低運算複雜度之通道估測法。藉由軟體無線電概念的引入，吾人所設計之收發機架構可有效地實現多模式傳輸功能。最後，吾人以電腦模擬驗證上述架構在無線通訊環境中具有優異的效能。

The development of wireless communication systems for high data rate transmission between terminals has become one of the new challenging subjects in the telecommunication research area. Multiple input multiple output (MIMO) techniques can create independent parallel channels in spatial domain for sending multiple data streams, thereby increasing the overall transmission rate of the system. Techniques of spatial multiplexing offered by MIMO can effectively enhance the spectral efficiency without the need of extra frequency resources. On the other hand, orthogonal frequency division multiplexing (OFDM) and code division multiple access (CDMA) are two popular transmission techniques in wireless communication. In this thesis, we investigate the joint design of OFDM and CDMA transceivers under the MIMO system architecture. The joint design is developed based on the idea of viewing OFDM subcarriers as a counterpart of CDMA spreading codes. Channel estimation and synchronization schemes for the jointly designed transceiver are also investigated in this thesis. In particular, we propose a frequency offset estimation scheme with a wider range of estimation and a channel estimation scheme with lower computational complexity. By the concept of software defined radio, multimode transmission can be carried out on the jointly designed transceiver architecture. Finally, the jointly designed transceiver is verified to possess good performance in wireless communication environments by computer simulations.